EP1183276B3 - Method for producing compacted free-flowing raw materials for varnish - Google Patents

Abstract

A process for producing compacted free-flowing nitrocellulose based lacquer raw materials is described. The process involves pressing a nitrocellulose based lacquer feed material, which is moistened with alcohol or water, through the holes of a die. The pressing step may be performed by means of at least one circulating breaker. The process optionally comprises shearing off the compacted lacquer raw material into pieces of selected length, below the die. The compacted nitrocellulose based lacquer raw materials prepared by the process of the present invention are free flowing and have a moisture content of at least 25%.

Description

The present invention relates to a process for producing compacted free-flowing water or alcohol wet nitrocellulose by pressing them through a perforated plate.

Low-esterified nitrocelluloses with up to 12.6% nitrogen content, which are mainly used in the paint industry, are prepared by esterification of celluloses with nitrating acids, which usually consist of a mixture of nitric acid, sulfuric acid and water.

After the nitrating acid, usually by intensive water washing, removed and adjusted by a thermal degradation process, the desired molecular weight of nitrocellulose must be phlegmatized to avoid auto-ignition, the resulting nitrocellulose, which is of fibrous structure. For this purpose, different phlegmatizers are used.

In addition to the incorporation of plasticizers, the humidification of nitrocellulose with alcohols and / or water is the most common method. The nitrocelluloses are usually commercialized with moisture contents of the alcohols (such as ethanol, isopropanol or butanol) and / or water of 30 and 35%, respectively. If it falls below a moistening level of 25%, these low-esterified nitrocelluloses are to be treated as "explosive substances" due to the increased risk potential (redcommendations on the Transport of Dangerous Goods, 10th edition of the United Nations (1997).

The fibrous nitrocelluloses, on account of their wool-like structure, have bulk densities of between 250 and 350 g / l on average. For the shipment of such products, the low bulk density has an unfavorable effect on packaging and shipping costs. This is counteracted by placing the fibrous nitrocellulose in the packaging container, e.g. a drum or a carton, is tamped. In this way, although it increases the bulk density, but at the same time worsens the flowability of nitrocellulose. This leads to an increased workload when emptying the nitrocellulose containers.

The EP-A-137 357 discloses a method for producing compressed nitrocellulose wherein the nitrocellulose is printed by means of a screw extruder into a thread which is then cut into sections.

A process for treating fibrous nitrocelluloses is known to make them safer for transport and storage ( GB-B-871 299 ). For compaction, a compressive force P = 2M + 6400 is exerted on the wet, fibrous nitrocellulose, where P is the force in pounds per square inch and M is the mean fiber length of the nitrocellulose in microns. The force, preferably between 15,000 and 17,000 psi (1,110-1,196 Kp / cm ² ), is applied by two non-spaced counter rotating rolls.

The resulting sheet-like nitrocellulose must then be broken into smaller pieces in an aggregate. A major disadvantage of this method is - in addition to the high investment and operating costs - dehumidifying the nitrocellulose during roll compaction. In the GB PS 871 299 All densified nitrocelluloses obtained by way of example have a moistening content of less than 25% and are consequently explosives. Practice has shown that in the roller compaction under the action of high pressures it comes to self-ignition, which is a danger to humans and equipment, especially as there is always a larger amount of nitrocellulose in the nip.

A similar process principle is used in the U.S. Patent 5,378,826 described. Again, the above-mentioned disadvantages apply.

It was therefore an object of the present invention to provide a novel process for producing compacted free-flowing nitrocellulose, which avoids dehydration of the nitrocellulose.

It has now surprisingly been found that compressed nitrocellulose can also be obtained in that in a mulling the circulating Koller (wheels) which run on a perforated die (plate), the moistened nitrocellulose through the holes (eg holes) of the die press (s. Fig. 1 ). The lacquer raw material nitrocellulose is thereby compacted. Below the die is a shearing device, with which the granular moldings are brought to the desired length. The cross-sectional shape of the moldings is determined by the shape of the hole cross-section.

It should be emphasized that, while maintaining certain process partners almost no dehumidification of the nitrocellulose used takes place and thus this does not come into the explosive area under 25% humidification.

At least 1 Koller runs in the mullion. Usual are 2 Koller; but it can also be more than 2 Koller. This depends on the size of the unit and the diameter of the Koller. The resulting compacted material can be hard (sharp edges) to soft (easily crushable by fingers).

But it is also possible that on a straight perforated die a wheel in the reciprocation of the moistened nitrocellulose presses through the die and thereby compacted.

For the consistency of the densified nitrocellulose, the compression ratio P is responsible for circular holes in the die. P is defined as the ratio of the length of the hole to the diameter of the hole in the die: $$\mathrm{P}\mathrm{=}\frac{\mathrm{Length\; of\; the\; hole}}{\mathrm{Diameter\; of\; the\; hole}}$$

The pressing ratio P should be between 0.5 and 5.0, preferably between 0.5 and 3.0.

It is also possible that the holes in the die have a square, rectangular, oval or irregular shaped cross-section. The number of holes per unit area of the die depends on the stability of the die. By compaction, it is possible to increase the bulk density of the nitrocellulose used many times and thereby obtain a free-flowing (free-flowing) material.

The uncompacted material is fed into the muller thread via a dosing device (such as screw, belt). It is also possible to render the pug mill inert, e.g. with nitrogen or carbon dioxide. The following examples are intended to describe but not limit the process.

FIG. 1:

1. (1): drive shaft
2. (2): Koller
3. (3): template with holes
4. (4): shearing device
5. (5): housing

• d: bore diameter
• e: bore length
• D _K: Koller diameter
• B: Cutter width
• D _M : die diameter

example 1

Nitrocellulose of standard A 30, moistened with 34.6% ethanol, is continuously added at 210 kg / h into the edge mill (die diameter: D _M = 175 mm, diameter of the roll: D _K = 130 mm, width of the wringer: B = 27 mm, number of rolls : 2, drive shaft speed = 150 min). The pressing ratio was 2 (hole diameter: d = 6 mm, hole shape: circular, length of the hole: 1 = 12 mm). The distance of the shearing device to the bottom of the die was 20 mm. The compacted product has a moisture content of 34.2% and a bulk density of 578 g / l. The moldings remained free-flowing even after being stored for eight weeks in a 110 l drum.

Example 2-7

The examples were carried out according to Example 1. The experimental parameters are summarized in Table 1. example NC Normty p moistening humidity throughput bulk weight die Drive shafts speed (min ^-1 ) in front (%) to (%) Wet NC (kg / h) before (gl / l) after (g / l) D (mm) L (mm) P 1 A 30 ethanol 34.6 34.2 210 383 578 6 12 2 150 2 E 27 ethanol 32.4 31.5 116 253 565 6 12 2 150 3 E 22 ethanol 32.0 31.7 130 196 556 10 20 2 150 4 E 34 ethanol 34.1 31.9 332 438 602 10 20 2 150 5 E 24 isopropanol 35.2 35.0 190 191 556 8th 16 2 150 6 A 27 ethanol 30.9 30.4 133 380 539 6 6 1 150 7 E 22 ethanol 32.8 31.7 57 196 526 6 6 1 201

Claims (6)

1. Method of producing compacted free-flowing varnish base materials based on nitrocellulose, characterized in that water-moist or alcohol-moist varnish base material is pressed through a die provided with holes, where there is no drying-out of the employed nitrocellulose to a value of less than 25 % moisture.
2. Method according to claim 1, characterized in that the pressing ratio P $$\mathrm{P}\mathrm{=}\frac{\mathrm{bore\; length}}{\mathrm{bore\; diameter}}=0.5-5.0,$$

   

   
   preferably between 0.5 and 3.0.
3. Method according to one of claims 1 and 2, characterized in that the varnish base material is pressed through the die holes by means of one or more rotating runners.
4. Method according to one of claims 1 or 2, characterized in that the varnish base material is pressed through the die holes by means of one or more oscillating wheels.
5. Method according to any one of claims 1 to 4, characterized in that the compacted varnish base material is sheared below the die into sections of desired length.
6. Method for producing granular varnish base materials, characterized in that the water-moist or alcohol moist nitrocellulose used as varnish base material has a nitrogen content ≤ 12.6 %.

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